Terminal and transmission method

ABSTRACT

In the present invention, regarding a narrowband used in a subframe for transmitting uplink data, if a switch is made from a first narrowband used in a first subframe to a second narrowband that is different from the first narrowband, with respect to a second subframe continuing to the first subframe, a final one symbol of the first subframe and an initial one symbol of the second subframe are punctured and set as a retuning time to transmit the uplink data in the first narrowband and the second narrowband.

TECHNICAL FIELD

The present disclosure relates to a terminal and a transmission method.

BACKGROUND ART

In 3GPP LTE (3rd Generation Partnership Project Long Term Evolution),OFDMA (Orthogonal Frequency Division Multiple Access) is adopted as acommunication scheme for a downlink from a base station (also referredto as an eNB) to a terminal (also referred to as a UE (User Equipment))is adopted, and SC-FDMA (Single Carrier-Frequency Division MultipleAccess) is adopted as a communication scheme for an uplink from aterminal to a base station (see, for example, NPLs 1 to 3).

In LTE, a base station performs communication by assigning an RB(Resource Block) in a system band to a terminal on a time unit basis,the time unit being called a subframe. FIG. 1 shows a configurationexample of a subframe of an LTE uplink shared channel (PUSCH: PhysicalUplink Shared Channel). As shown in FIG. 1, one subframe is made up oftwo time slots. In each slot, a plurality of SC-FDMA data symbols andDMRS's (Demodulation Reference Signals) are time-multiplexed. Uponreceipt of a PUSCH, the base station performs channel estimation usingthe DMRS's. After that, the base station performs demodulation/decodingof the SC-FDMA data symbols using a result of the channel estimation.

Further, in LTE, HARQ (Hybrid Automatic Repeat Request) is applied todownlink data. In other words, a terminal feeds back a response signalindicating an error detection result of downlink data to a base station.The terminal performs CRC (Cyclic Redundancy Check) for the downlinkdata, and feeds back an acknowledgement (ACK) if there is not an errorin an operation result of the CRC and a negative acknowledgement (NACK)if there is an error in the operation result of the CRC, to the basestation as the response signal. An uplink control channel such as aPUCCH (Physical Uplink Control Channel) is used to feed back thisresponse signal (that is, the ACK/NACK signal).

A plurality of formats are selectively used according to situations ofthe terminal transmitting the ACK/NACK signal through the PUCCH. Forexample, if there is not control information to be transmitted otherthan the ACK/NACK signal and an uplink scheduling request, a PUCCHformat 1a/1b is used. On the other hand, if transmission of the ACK/NACKsignal overlaps with feedback of CSI (Channel State Information) whichis periodically transmitted through an uplink channel, a PUCCH format2a/2b is used.

As shown in FIG. 2, each of a plurality of ACK/NACK signals transmittedfrom a plurality of terminals in the PUCCH format 1a/1b is spread by aZAC (Zero Auto-Correlation) sequence having a Zero Auto-correlationcharacteristic (multiplied by the ZAC sequence) on a time axis and iscode-multiplexed in the PUCCH. In FIG. 2, (W(0), W(1), W(2), W(3))indicates a Walsh sequence with a sequence length of 4, and (F(0), F(1),F(2)) indicates a DFT (Discrete Fourier Transform) sequence with asequence length of 3.

As shown in FIG. 2, first in a terminal, the ACK/NACK signal isprimarily spread to frequency components each of which corresponds toone SC-FDMA symbol by the ZAC sequence (with a sequence length of 12) ona frequency axis. In other words, the ZAC sequence with a sequencelength of 12 is multiplied by ACK/NACK signal components each of whichis represented by a complex number. Next, each of the primarily spreadACK/NACK signal and the ZAC sequence as a reference signal aresecondarily spread by the Walsh sequence (with a sequence length of 4;W(0) to W(3)) and the DFT sequence (with a sequence length of 3; F(0) toF(2)), respectively. In other words, components of the signal with asequence length of 12 (the primarily spread ACK/NACK signal or the ZACsequence as a reference signal) are multiplied by components of anorthogonal cover code (OCC) sequence (the Walsh sequence or the DFTsequence), respectively. Furthermore, the secondarily spread signals areconverted to signals with a sequence length of 12 on the time axis byIDFT (Inverse Discrete Fourier Transform) or IFFT (Inverse Fast FourierTransform). Then, a CP (Cyclic Prefix) is added to each of the signalsafter the IFFT, and a 1-slot signal composed of seven SC-FDMA symbols isformed.

Further, as shown in FIG. 3, a PUCCH is assigned to each terminal insubframes.

ACK/NACK signals from different terminals are spread (multiplexed) withZAC sequences defined by different cyclic shift indexes or orthogonalcover code sequences corresponding to different sequence numbers(orthogonal cover (OC) indexes). An orthogonal cover code sequence is aset of a Walsh sequence and a DFT sequence. Further, the orthogonalcover code sequence may be referred to as a block-wise spreading codesequence. Therefore, a base station can separate the plurality ofcode-multiplexed ACK/NACK signals by using conventional despreading andcorrelation processing (see, for example, NPL 4).

By the way, recently, M2M (Machine-to-Machine) communication ispromising which realizes services by autonomous communication amongpieces of equipment without judgment of users as a structure supportinga future information society. A specific application example of an M2Msystem includes a smart grid. The smart grid is an infrastructure systemfor efficiently supplying lifelines such as electricity and gas. Forexample, the smart grid performs M2M communication between a smartmeterdisposed in each home or building and a central server to autonomouslyand efficiently adjust demand balance of resources. Other applicationexamples of the M2M communication system include a monitoring system forarticle management, environmental sensing or telemedicine, remotemanagement of stock or charging for vending machines, and the like.

As for the M2M communication system, attention has been paid especiallyto utilization of a cellular system having an extensive communicationarea. In 3GPP, standardization of enhancement of a cellular network forM2M called MTC (Machine Type Communication) has been promoted (see, forexample, NPL 5) in standardization of LTE and LTE-Advanced, andexamination of specifications has been started, with cost reduction,power consumption reduction and coverage enhancement as requirements.Especially, in the case of terminals, such as smartmeters, which arevirtually immobile unlike handset terminals which are often used byusers while the users are moving, it is necessary to secure coverage toprovide services. Therefore, in order to support a case where, at aplace in an existing LTE and LTE-Advanced communication area where anLTE or LTE-Advanced terminal cannot be used, such as the underground ofa building, a terminal (an MTC terminal) usable at such a place isdisposed, “coverage enhancement (MTC coverage enhancement)” to furtherexpand a communication area has been examined.

CITATION LIST Non-Patent Literature

NPL 1

3GPP TS 36.211 V12.7.0, “Evolved Universal Terrestrial Radio Access(E-UTRA); Physical channels and modulation (Release 12),” September 2015

NPL 2

3GPP TS 36.212 V12.6.0, “Evolved Universal Terrestrial Radio Access(E-UTRA); Multiplexing and channel coding (Release 12),” September 2015

NPL 3

3GPP TS 36.213 V12.7.0, “Evolved Universal Terrestrial Radio Access(E-UTRA); Physical layer procedures (Release 12),” September 2015

NPL 4

Seigo Nakao, Tomofumi Takata, Daichi Imamura, and Katsuhiko Hiramatsu,“Performance enhancement of E-UTRA uplink control channel in fast fadingenvironments,” Proceeding of 2009 IEEE 69th Vehicular TechnologyConference (VTC2009-Spring), April 2009

NPL 5

RP-141660, Ericsson, Nokia Networks, “New WI proposal: Further LTEPhysical Layer Enhancements for MTC,” September 2014

NPL 6

R1-151454, MCC Support, “Final Report of 3GPP TSG RAN WG1 #80 v1.0.0,”February 2015

NPL 7

R1-155051, RAN4, Ericsson, “Reply LS on retuning time between narrowbandregions for MTC,” August 2015

SUMMARY OF INVENTION

In MTC coverage extension, “repetition” technology of repeatedlytransmitting the same signal a plurality of times is examined in orderto further expand a communication area. In the repetition, by combiningsignals which have been repetition-transmitted on the transmission side,received signal power is improved, and coverage (a communication area)is expanded.

In MTC for which examination of specifications of LTE-Advanced Release13 (Rel-13) is promoted, a terminal (hereinafter also referred to as anMTC terminal) supports only a frequency bandwidth of 1.4 MHz (alsoreferred to as a narrowband or a narrowband region) in order to realizereduction in cost of the terminal. Therefore, “frequency hopping” isintroduced in which the 1.4-MHz frequency band to be used by theterminal for transmission is hopped for every predetermined number ofsubframes within a system band (see, for example, NPL 6). At the time offrequency hopping, carrier frequency retuning time is required. It isthought that time corresponding to up to about two symbols is requiredas the retuning time (see, for example, NPL 7).

In a downlink, since a Rel-13 MTC terminal does not receive an existingLTE downlink control channel (PDCCH: Physical Downlink Control Channel),the first two OFDM symbols of a subframe which is an existing LTE PDCCHregion can be used for the retuning time.

On the other hand, in an uplink, the Rel-13 MTC terminal can transmit aPUSCH or a PUCCH using all SC-FDMA symbols in a subframe, similarly toan existing LTE terminal. Therefore, in order to apply frequency hoppingto the MTC terminal, it is necessary to, at the time of retuning, stoptransmission of a part of the PUSCH or the PUCCH to secure retuning timecorresponding to about two SC-FDMA symbols. It is necessary to suppressdeterioration of transmission characteristics while securing theretuning time for an uplink signal (PUSCH or PUCCH).

A terminal according to an aspect of the present disclosure adopts aconfiguration provided with: a control section that, if, for anarrowband to be used for a subframe to transmit uplink data, switchingfrom a first narrowband used for a first subframe to a second narrowbanddifferent from the first narrowband, for a second subframe following thefirst subframe, punctures a last one symbol of the first subframe and afirst one symbol of the second subframe to set the symbols as retuningtime; and a transmitting section that transmits the uplink data in thefirst narrowband and the second narrowband.

Comprehensive or specific aspects of the above may be realized by asystem, a method, an integrated circuit, a computer program or arecording medium or may be realized by an arbitrary combination of asystem, an apparatus, a method, an integrated circuit, a computerprogram and a recording medium.

According to one aspect of the present disclosure, it is possible tosecure retuning time while suppressing deterioration of transmissioncharacteristics of an uplink signal (PUSCH or PUCCH).

Further advantages and effects of the one aspect of the presentdisclosure will be made clear from the specification and accompanyingdrawings. Such advantages and/or effects are provided by someembodiments and features shown in the specification and the accompanyingdrawings. It is not necessarily required that all of them are providedto obtain one or more same features.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example of a configuration of a PUSCH subframe;

FIG. 2 illustrates an example of a response signal generation process ina PUCCH;

FIG. 3 illustrates an example of a configuration of a PUCCH format 1a/1bsubframe;

FIG. 4 illustrates an example of setting retuning time (Method 1);

FIG. 5 illustrates an example of setting retuning time (Method 2);

FIG. 6 illustrates an example of setting retuning time (Method 3);

FIG. 7 illustrates an example of setting retuning time (Method 4);

FIG. 8 is a block diagram showing a configuration of a main part of aterminal according to Embodiment 1;

FIG. 9 is a block diagram showing a configuration of a base stationaccording to Embodiment 1;

FIG. 10 is a block diagram showing a configuration of the terminalaccording to Embodiment 1;

FIG. 11 illustrates an example of frequency hopping according toEmbodiment 1;

FIG. 12 illustrates an example of frequency hopping according toEmbodiment 2;

FIG. 13 illustrates an example of mapping of an ACK/NACK signalaccording to Embodiment 2;

FIG. 14 illustrates an example of frequency hopping according toEmbodiment 3;

FIG. 15 illustrates an example of frequency hopping according to amodification of Embodiment 2 or 3;

FIG. 16 illustrates an example of frequency hopping according toEmbodiment 4;

FIG. 17 illustrates an example of frequency hopping according toEmbodiment 4;

FIG. 18 illustrates an example of frequency hopping according toEmbodiment 5;

FIG. 19 illustrates an example of frequency hopping according toEmbodiment 5; and

FIG. 20 illustrates an example of a configuration of a PUCCH format2/2a/2b subframe.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described in detail withreference to accompanying drawings.

[One Piece of Knowledge which Became Basis of Present Disclosure]

As described above, in a downlink, since a Rel-13 MTC terminal does notreceive an existing LTE down link control channel (PDCCH: PhysicalDownlink Control Channel), the first two OFDM symbols of a subframewhich is an existing LTE PDCCH region can be used as the retuning time.

On the other hand, in an uplink, the Rel-13 MTC terminal can transmit aPUSCH or a PUCCH using all SC-FDMA symbols in a subframe, similarly toan existing LTE terminal. Therefore, in order to apply frequency hoppingto the MTC terminal, it is necessary to, at the time of retuning, stoptransmission of a part of the PUSCH or the PUCCH to secure retuning timecorresponding to about two SC-FDMA symbols.

As a method for securing retuning time for an uplink, four Methods 1 to4 shown below will be described.

Method 1 (FIG. 4): a method in which last two SC-FDMA symbols of onesubframe immediately before retuning are discarded (punctured) and usedfor retuning time;

Method 2 (FIG. 5): a method in which first two SC-FDMA symbols of onesubframe immediately after retuning are discarded and used for retuningtime;

Method 3 (FIG. 6): a method in which the last SC-FDMA symbol of onesubframe immediately before retuning and the first SC-FDMA symbol of onesubframe immediately after retuning are discarded and used for retuningtime; and

Method 4 (FIG. 7): a method in which a guard subframe (one subframe) forretuning is provided.

Among the methods for securing retuning time described above, Method 4requires retuning time corresponding to one subframe each time frequencyhopping is performed. Therefore, in comparison with the other Methods 1to 3, time (or the number of subframes) required to complete allrepetition transmissions increases, and resource use efficiencydecreases.

For example, when a frequency hopping period is Y subframes, theresource use efficiency in Method 4 is (Y−1)/Y. On the other hand, theresource use efficiency in Methods 1 to 3 is (Y−1+(12/14))/Y. Therefore,for example, in the case of Y=4, the resource use efficiency can beimproved by about 28% in Methods 1 to 3 in comparison with Method 4.

There are two methods shown below as formats for transmitting data in aretuning subframe (a subframe one or two SC-FDMA symbols of which are tobe used for retuning time) at the time of PUSCH repetition in Methods 1to 3.

The first method is a method in which, after mapping data to twelveSC-FDMA symbols excluding DMRS's as shown in FIG. 1 similarly to othersubframes, an SC-FDMA symbol (or symbols) for retuning time ispunctured. In this method, in a retuning subframe and in othersubframes, the same signal is transmitted in symbols other than theSC-FDMA symbol (or symbols) punctured for retuning time is transmitted.Therefore, coherent combining can be easily realized on the base stationside.

The second method is a method in which, as a format for transmittingdata in a retuning subframe, a data encoding rate is changed to bedifferent from that for other subframes, and data is mapped to ten oreleven SC-FDMA symbols excluding the SC-FDMA symbol (or symbols) forretuning time (rate matching). This method is used in existing LTE whichdoes not assume repetition transmission, and, therefore, change fromexisting standards is not required. Since a different signal istransmitted in each symbol, in the retuning subframe (subframes) and inthe other subframes, coherent combining cannot be performed on the basestation side.

Since neither of the methods influences much on data transmission in aPUSCH, it is desirable to use any of Methods 1 to 3 in PUSCH repetitionfrom a view point of the resource use efficiency.

Further, at the time of PUCCH repetition also, it is desirable to useany of Methods 1 to 3 from the view point of the resource use efficiencyand a view point of commonness between operations of the PUCCH and thePUSCH. In Methods 1 to 3, however, since a part of an SC-FDMA symbolencoded with an OCC (Orthogonal Cover Code) sequence is not used,collapse of orthogonality between orthogonal sequences occurs, and thereis a possibility that characteristics deteriorate due to interferenceamong codes.

Therefore, in one aspect of the present disclosure, a terminal and atransmission method which are capable of securing retuning time whilesuppressing deterioration of transmission characteristics of an uplinksignal (PUSCH or PUCCH) are provided.

[Outline of Communication System]

A communication system according to each embodiment of the presentdisclosure is provided with base station 100 and terminal 200 which are,for example, compatible with an LTE-Advanced system. Terminal 200 is anMTC terminal.

FIG. 8 is a block diagram showing a configuration of a main part ofterminal 200 according to each embodiment of the present disclosure. Interminal 200 shown in FIG. 8, spreading section 215 spreads an ACK/NACKsignal for downlink data using any one of a plurality of orthogonalcover code sequences (OCC sequences). Repetition section 216 performsrepetition over a plurality of subframes of the spread ACK/NACK signal.Signal assigning section 217 maps the repeated ACK/NACK signal to anarrowband for MTC terminals. If narrowbands to be used for a firstsubframe and a second subframe following the first subframe, among aplurality of subframes, are different (that is, in the case ofperforming retuning), control section 209 punctures the last two symbolsof the first subframe or the first two symbols of the second subframe.Transmitting section 220 transmits the ACK/NACK signal in thenarrowband. Each of the plurality of orthogonal cover code sequences ismade up of a first partial sequence composed of codes corresponding tothe first two symbols of a subframe and a second partial sequencecomposed of codes corresponding to the last two symbols, and, among theplurality of orthogonal cover code sequences, the first partialsequences and the second partial sequences are partially orthogonal toone another.

Embodiment 1

[Configuration of Base Station]

FIG. 9 is a block diagram showing a configuration of base station 100according to Embodiment 1 of the present disclosure. In FIG. 9, basestation 100 has control section 101, control signal generating section102, control signal encoding section 103, control signal modulatingsection 104, data encoding section 105, retransmission control section106, data modulating section 107, signal assigning section 108, IFFT(Inverse Fast Fourier Transform) section 109, CP (Cyclic Prefix) addingsection 110, transmitting section 111, antenna 112, receiving section113, CP removing section 114, FFT (Fast Fourier Transform) section 115,extracting section 116, demapping section 117, channel estimatingsection 118, equalizing section 119, demodulating section 120, decodingsection 121, judging section 122, despreading section 123, correlationprocessing section 124 and judging section 125.

Control section 101 decides assignment of a PDSCH and a PUSCH toterminal 200. At this time, control section 101 decides frequencyassignment resources, modulation/encoding methods and the like to bespecified to terminal 200 and outputs information about the decidedparameters to control signal generating section 102.

Further, control section 101 decides a coding rate for a control signaland outputs the decided coding rate to control signal encoding section103. Further, control section 101 decides radio resources (downlinkresources) to which the control signal and downlink data are to bemapped and outputs information about the decided radio resources tosignal assigning section 108. Further, control section 101 decides acoding rate to be used at the time of transmitting the downlink data(data to be transmitted) for terminal 200, which is a resourceassignment target, and outputs the decided coding rate to data encodingsection 105.

Further, control section 101 decides a coverage enhancement level ofterminal 200 (an MTC terminal) and outputs information about the decidedcoverage enhancement level or the number of repetitions required forPUSCH transmission or PUCCH transmission at the decided coverageenhancement level to control signal generating section 102 andextracting section 116. Further, control section 101 decides a frequencyhopping method (on/off of frequency hopping, a frequency hopping periodand the like) for PUSCH repetition transmission or PUCCH repetitiontransmission and outputs information about the decided frequency hoppingmethod to control signal generating section 102.

Further, control section 101 decides resources (a cyclic shift, anorthogonal cover code sequence and a frequency) for terminal 200 totransmit a PUCCH. Control section 101 outputs an amount of cyclic shift(a ZAC sequence) which may be used for PUCCH transmission and theorthogonal cover code sequence to despreading section 123 andcorrelation processing section 124, respectively, and outputsinformation about frequency resources to be used for PUCCH transmissionto extracting section 116. These pieces of information about PUCCHresources may be implicitly notified to terminal 200 or may be notifiedto terminal 200 (control section 209 to be described later) by signalingby a higher layer signaling to terminal 200.

Control signal generating section 102 generates a control signal forterminal 200. The control signal includes a signal of a cell-specifichigher layer, a signal of a UE-specific higher layer, an uplink grantindicating assignment of a PUSCH or downlink assignment informationindicating assignment of a PDSCH.

The uplink grant is made up of a plurality of bits and includesinformation indicating frequency assignment resources, modulation/codingschemes and the like. Further, the uplink grant may include informationabout a coverage enhancement level or information about the number ofrepetitions required for PUSCH transmission.

The downlink assignment information is made up of a plurality of bitsand includes information indicating frequency assignment resources,modulation/coding schemes and the like. Further, the downlink assignmentinformation may include information about a coverage enhancement levelor information about the number of repetitions required for PUCCHtransmission.

Control signal generating section 102 generates a control informationbit sequence using control information inputted from control section 101and outputs the generated control information bit sequence (a controlsignal) to control signal encoding section 103. Since the controlinformation may be transmitted to a plurality of terminals 200, controlsignal generating section 102 includes a UE ID of each terminal 200 incontrol information for terminal 200 to generate a bit sequence. Forexample, a CRC (Cyclic Redundancy Check) bit masked by a UE ID of adestination terminal is added to the control information.

Control signal encoding section 103 encodes the control signal (thecontrol information bit sequence) received from control signalgenerating section 102 according to the encoding rate specified fromcontrol section 101 and outputs the encoded control signal to controlsignal modulating section 104.

Control signal modulating section 104 modulates the control signalreceived from control signal encoding section 103 and outputs themodulated control signal (a symbol sequence) to signal assigning section108.

Data encoding section 105 performs error correction coding with a Turbocode or the like for transmit data (downlink data) according to thecoding rate received from control section 101 and outputs a data signalafter the encoding to retransmission control section 106.

At the time of initial transmission, retransmission control section 106holds the data signal after the encoding received from data encodingsection 105 and also outputs the data signal to data modulating section107. Retransmission control section 106 holds the data signal after theencoding for each destination terminal. Further, upon receipt of a NACKto the transmitted data signal from judging section 125, retransmissioncontrol section 106 outputs corresponding data which it holds to datamodulating section 107. Upon receipt of an ACK to the transmitted datasignal from judging section 125, retransmission control section 106deletes the corresponding data which it holds.

Data modulating section 107 modulates the data signal received fromretransmission control section 106 and outputs the modulated data signalto signal assigning section 108.

Signal assigning section 108 maps the control signal (the symbolsequence) received from control signal modulating section 104 and themodulated data signal received from data modulating section 107 to theradio resources specified from control section 101. A control channel towhich the control signal is to be mapped may be either a PDCCH for MTC(a downlink control channel) or an EPDCCH (an Enhanced PDCCH). Signalassigning section 108 outputs a signal of downlink subframes whichinclude a PDCCH for MTC or an EPDCCH to which the control signal ismapped, to IFFT section 109.

IFFT section 109 converts a frequency domain signal to a time domainsignal by performing IFFT processing for the signal received from signalassigning section 108. IFFT section 109 outputs the time domain signalto CP adding section 110.

CP adding section 110 adds a CP to the signal received from IFFT section109 and outputs the signal to which CP is added (an OFDM signal) totransmitting section 111.

Transmitting section 111 performs RF (Radio Frequency) processing suchas D/A (Digital-to-Analog) conversion and upconversion for the OFDMsignal received from CP adding section 110 and transmits a radio signalto terminal 200 via antenna 112.

Receiving section 113 performs RF processing such as downconversion andA/D (Analog-to-Digital) conversion for an uplink signal (PUSCH or PUCCH)from terminal 200 received via antenna 112 and outputs an obtainedreceived signal to CP removing section 114. The uplink signal (PUSCH orPUCCH) transmitted from terminal 200 includes a repetition-processedsignal over a plurality of subframes.

CP removing section 114 removes a CP added to the received signalreceived from receiving section 113 and outputs the signal from whichthe CP has been removed, to FFT section 115.

FFT section 115 applies FFT processing to the signal received from CPremoving section 114, transforms the signal into a frequency-domainsignal sequence and takes out a signal corresponding to PUSCH or PUCCHsubframes. FFT section 115 outputs the obtained signal to extractingsection 116.

Extracting section 116 extracts a PUSCH or a PUCCH based on informationabout PUSCH or PUCCH resources inputted from control section 101.Further, extracting section 116 combines the plurality of subframes ofthe PUSCH or the PUCCH which have been repetition-transmitted, usinginformation about the repetition transmission of the PUSCH or the PUCCH(repetition information) inputted from control section 101. Extractingsection 116 outputs the combined signal to demapping section 117.

Demapping section 117 extracts a PUSCH portion assigned to terminal 200from the signal received from extracting section 116. Further, demappingsection 117 disassembles the extracted PUSCH for terminal 200 intoDMRS's and data symbols, outputs the DMRS's to channel estimatingsection 118 and outputs the data symbols (SC-FDMA data symbols) toequalizing section 119. Further, demapping section 117 disassembles thePUCCH received from extracting section 116 into DMRS's and an ACK/NACKsignal, outputs the DMRS's to channel estimating section 118 and outputsthe ACK/NACK signal to equalizing section 119.

Channel estimating section 118 performs channel estimation using theDMRS's inputted from demapping section 117. Channel estimating section118 outputs an obtained channel estimate to equalizing section 119.

Equalizing section 119 performs equalization of the SC-FDMA data symbolsor the ACK/NACK signal inputted from demapping section 117 using thechannel estimate inputted from channel estimating section 118.Equalizing section 119 outputs the equalized SC-FDMA data symbols todemodulating section 120 and outputs the equalized ACK/NACK signal todespreading section 123.

Demodulating section 120 applies IDFT to the frequency-domain SC-FDMAdata symbols inputted from equalizing section 119 to convert thefrequency-domain SC-FDMA data symbols to a time domain signal (a symbolsequence) and, after that, performs data demodulation. Specifically,demodulating section 120 converts the symbol sequence to a bit sequencebased on a modulation scheme specified to terminal 200 and outputs theobtained bit sequence to decoding section 121.

Decoding section 121 performs error correction decoding for the bitsequence inputted from demodulating section 120 and outputs the decodedbit sequence to judging section 122.

Judging section 122 performs error detection for the bit sequenceinputted from decoding section 121. The error detection is performedusing a CRC bit added to the bit sequence. If a result of judgment ofthe CRC bit indicates that there is no error, judging section 122 takesout receive data and notifies control section 101 of an ACK (not shown).On the other hand, if the result of the judgment of the CRC bitindicates that there is an error, judging section 122 notifies controlsection 101 of a NACK (not shown).

Despreading section 123 despreads a signal of a part of the signalreceived from equalizing section 119, which corresponds to the ACK/NACKsignal, using an orthogonal cover code sequence (an orthogonal covercode sequence which terminal 200 should use) received from controlsection 101 and outputs the despread signal to correlation processingsection 124.

Correlation processing section 124 determines a correlation valuebetween the ZAC sequence (a ZAC sequence which terminal 200 may use; theamount of cyclic shift) inputted from control section 101 and the signalinputted from despreading section 123 and outputs the correlation valueto judging section 125.

Judging section 125 judges which of ACK and NACK the ACK/NACK signaltransmitted from terminal 200 shows for the transmitted data, based onthe correlation value received from correlation processing section 124.Judging section 125 outputs a judgment result to retransmission controlsection 106.

[Configuration of Terminal]

FIG. 10 is a block diagram showing a configuration of terminal 200according to Embodiment 1 of the present disclosure. In FIG. 9, terminal200 has antenna 201, receiving section 202, CP removing section 203, FFTsection 204, extracting section 205, data demodulating section 206, datadecoding section 207, CRC section 208, control section 209, dataencoding section 210, CSI signal generating section 211, response signalgenerating section 212, modulating section 213, DFT section 214,spreading section 215, repetition section 216, signal assigning section217, IFFT section 218, CP adding section 219 and transmitting section220.

Receiving section 202 performs RF processing such as downconversion orAD conversion for a radio signal (a PDCCH for MTC or EPDCCH) and a datasignal (a PDSCH) from base station 100 received via antenna 201 toobtain a baseband OFDM signal. Receiving section 202 outputs the OFDMsignal to CP removing section 203.

CP removing section 203 removes a CP added to the OFDM signal receivedfrom receiving section 202 and outputs the signal from which the CP hasbeen removed to FFT section 204.

FFT section 204 converts a time domain signal to a frequency domainsignal by performing FFT processing for the signal received from CPremoving section 203. FFT section 204 outputs the frequency domainsignal to extracting section 205.

Extracting section 205 extracts a PDCCH for MTC or EPDCCH from thefrequency domain signal received from FFT section 204, performs blinddecoding for the PDCCH for MTC or EPDCCH to attempt decoding of acontrol signal destined to its own terminal 200. A CRC masked by the UEID of terminal 200 is added to the control signal destined to terminal200. Therefore, if a CRC judgment indicates OK as a result of performingblind decoding, extracting section 205 extracts control information andoutputs the control information to control section 209. Further,extracting section 205 extracts downlink data (a PDSCH signal) from thesignal received from FFT section 204 and outputs the downlink data todata demodulating section 206.

Data demodulating section 206 demodulates the downlink data receivedfrom extracting section 205 and outputs the demodulated downlink data todata decoding section 207.

Data decoding section 207 decodes the downlink data received from datademodulating section 206 and outputs the decoded downlink data to CRCsection 208.

CRC section 208 performs error detection for the downlink data receivedfrom data decoding section 207 using CRC, and outputs an error detectionresult to response signal generating section 212. Further, if thedownlink data is judged to be without an error, CRC section 208 outputsthe downlink data as receive data.

Control section 209 performs control of PUSCH transmission based on thecontrol signal inputted from extracting section 205. Specifically,control section 209 specifies resource assignment at the time of PUSCHtransmission to signal assigning section 217 based on PUSCH resourceassignment information included in the control signal. Further, controlsection 209 specifies a coding scheme and a modulation scheme at thetime of PUSCH transmission to data encoding section 210 and modulatingsection 213, respectively, based on information about the coding schemeand the modulation scheme included in the control signal. Further,control section 209 decides the number of repetitions at the time ofPUSCH repetition transmission based on information about a coverageenhancement level or the number of repetitions required for PUSCHtransmission included in the control signal, and specifies informationabout the decided number of repetitions to repetition section 216.Further, control section 209 specifies frequency hopping for PUSCHrepetition to repetition section 216 based on information about afrequency hopping method included in the control signal.

Further, control section 209 performs control of PUCCH transmissionbased on the control signal inputted from extracting section 205.Specifically, control section 209 identifies PUCCH resources (afrequency, an amount of cyclic shift and an orthogonal cover codesequence) based on information about the PUCCH resources included in thecontrol signal, and specifies the identified information to spreadingsection 215 and signal assigning section 217. Further, control section209 decides the number of repetitions at the time of PUCCH repetitiontransmission based on information about a coverage enhancement level orinformation about the number of repetitions required for PUCCHtransmission, and specifies information about the decided number ofrepetitions to repetition section 216. Further, control section 209specifies frequency hopping for PUCCH repetition to repetition section216 based on the information about the frequency hopping method includedin the control signal. Further, control section 209 specifies atransmission format for each subframe in PUCCH repetition to spreadingsection 215.

Data encoding section 210 adds a CRC bit masked by the UE ID of terminal200 to inputted transmit data, performs error correction coding andoutputs an encoded bit sequence to modulating section 213.

CSI signal generating section 211 generates CSI feedback informationbased on a CSI measurement result of terminal 200 and outputs the CSIfeedback information to modulating section 213.

Response signal generating section 212 generates a response signal (anACK/NACK signal) to received downlink data (a PDSCH signal) based on anerror detection result received from CRC section 208. Specifically,response signal generating section 212 generates a NACK if an error isdetected, and generates an ACK if an error is not detected. Responsesignal generating section 212 outputs the generated ACK/NACK signal tomodulating section 213.

Modulating section 213 modulates the bit sequence received from dataencoding section 210 and outputs a modulated signal (a symbol sequence)to DFT section 214. Further, modulating section 213 modulates the CSIfeedback information received from CSI signal generating section 211 andthe ACK/NACK signal received from response signal generating section 212and outputs a modulated signal (a symbol sequence) to spreading section215.

DFT section 214 applies DFT to the signal inputted from modulatingsection 213 to generate a frequency domain signal, and outputs thefrequency domain signal to repetition section 216.

Spreading section 215 spreads a reference signal, and the CSI feedbackinformation and ACK/NACK signal received from modulating section 213,using a ZAC sequence defined by the amount of cyclic shift set bycontrol section 209 and an orthogonal cover code sequence, and outputsthe spread signal to repetition section 216. At this time, spreadingsection 215 spreads the ACK/NACK signal using the transmission formatfor each subframe in PUCCH repetition set by control section 209.

When its own terminal is in an MTC coverage enhancement mode, repetitionsection 216 performs repetition of a signal inputted from DFT section214 or spreading section 215 over a plurality of subframes, based on thenumber of repetitions specified from control section 209 to generate arepetition signal. Repetition section 216 outputs the repetition signalto signal assigning section 217.

Signal assigning section 217 maps the signal received from repetitionsection 216 to PUSCH or PUCCH time/frequency resources specified fromcontrol section 209. Signal assigning section 217 outputs a PUSCH orPUCCH signal to which the signal is mapped, to IFFT section 218.

IFFT section 218 generates a time domain signal by performing IFFTprocessing for the frequency domain PUSCH or PUCCH signal inputted fromsignal assigning section 217. IFFT section 218 outputs the generatedsignal to CP adding section 219.

CP adding section 219 adds a CP to the time domain signal received fromIFFT section 218 and outputs the signal to which the CP is added, totransmitting section 220.

Transmitting section 220 performs RF processing such as D/A conversionand upconversion for the signal received from CP adding section 219 andtransmits a radio signal to base station 100 via antenna 201.

[Operations of Base Station 100 and Terminal 200]

Operations of base station 100 and terminal 200 having the aboveconfigurations will be described in detail.

In the present embodiment, Method 1 (FIG. 4) or Method 2 (FIG. 5) amongMethods 1 to 4 for securing retuning time described above will be used.In other words, in the case of switching a narrowband to be used byfrequency hopping, terminal 200 (control section 209) may discard thelast two SC-FDMA data symbols of one subframe immediately beforeretuning to use the SC-FDMA data symbols for retuning time or maydiscard the first two SC-FDMA data symbols of one subframe immediatelyafter retuning to use the SC-FDMA data symbols for retuning time.

Base station 100 indicates terminal 200 of the number of PUSCHrepetitions (N_(PUSCH)) or the number of PUCCH repetitions (N_(PUCCH))in advance before PUSCH or PUCCH transmission/reception. The number ofrepetitions N_(PUSCH) or N_(PUCCH) may be indicated to terminal 200 frombase station 100 via a UE-specific higher layer or may be indicatedusing a PDCCH for MTC.

Further, base station 100 indicates terminal 200 of a frequency hoppingmethod (on/off of frequency hopping and a frequency hopping period Y) inadvance before PUSCH or PUCCH transmission/reception. The frequencyhopping period Y may be indicated to terminal 200 via a cell-specifichigher layer by base station 100 as a cell-specific parameter orindicated to terminal 200 via a UE-specific higher layer by base station100 as a UE-specific parameter. Further, the frequency hopping period Ymay be a parameter predefined according to standards.

Terminal 200 performs PUSCH or PUCCH repetition transmission for thenumber of times corresponding to the number of repetitions indicatedfrom base station 100 (N_(PUSCH) or N_(PUCCH)).

Further, if frequency hopping is on, and the number of repetitions(N_(PUSCH) or N_(PUCCH)) is larger than Y, terminal 200 changes a1.4-MHz frequency band which terminal 200 uses to transmit a repetitionsignal (performs frequency hopping) after transmitting a repetitionsignal in consecutive Y subframes using the same resources, andtransmits a repetition signal again in consecutive Y subframes using thesame resources. At the time of performing frequency hopping, terminal200 secures retuning time corresponding to two SC-FDMA data symbolsimmediately before or immediately after retuning according to Method 1(FIG. 4) or Method 2 (FIG. 5).

<In the Case of PUSCH Repetition>

At the time of PUSCH repetition, terminal 200 maps data to twelveSC-FDMA data symbols excluding DMRS's (see, for example, FIG. 1) in aretuning subframe (one subframe immediately before retuning in Method 1,and one subframe immediately after retuning in Method 2) and, afterthat, punctures two SC-FDMA data symbols for retuning time (the last twosymbols in the subframe in Method 1, and the first two symbols in thesubframe in Method 2).

Otherwise, terminal 200 maps the data to ten SC-FDMA data symbolsexcluding DMRS's and two SC-FDMA data symbols for retuning time in theretuning subframe (rate matching).

<In the Case of PUCCH Repetition>

At the time of PUCCH repetition, terminal 200 maps an ACK/NACK signaland a reference signal in a retuning subframe with a normal PUCCH formatand, after that, punctures two SC-FDMA symbols for retuning time.

FIG. 11 shows a state of frequency hopping in PUCCH repetition in thecase of Method 1 and Y=4. As shown in FIG. 11, upon transmission of arepetition signal in consecutive subframes of Y=4, terminal 200 changesa frequency band by frequency hopping and transmits a repetition signalagain in consecutive four subframes. In Method 1, terminal 200 puncturestwo SC-FDMA symbols of immediately before retuning (that is, the lasttwo) of one subframe immediately before retuning.

Further, in the present embodiment, terminal 200 limits the number ofcandidates for an orthogonal cover code sequence to be used to spread anACK/NACK signal to two.

For example, terminal 200 sets an orthogonal cover code sequence to beused to spread an ACK/NACK from between two candidates of (W(0), W(1),W(2), W(3))=(1, 1, 1, 1) and (1, −1, 1, −1) as candidates for anorthogonal cover code sequence or from between two candidates of (W(0),W(1), W(2), W(3))=(1, 1, 1, 1) and (1, −1, −1, 1).

Here, a partial sequence (1, 1) composed of two codes of the former halfof the orthogonal cover code sequence (1, 1, 1, 1) is orthogonal to eachof a partial sequence (1, −1) composed of two codes of the former halfof the orthogonal cover code sequence (1, −1, 1, −1) and a partialsequence (1, −1) composed of two codes of the former half of theorthogonal cover code sequence (1, −1, −1, 1). Further, a partialsequence (1, 1) composed of two codes of the latter half of theorthogonal cover code sequence (1, 1, 1, 1) is orthogonal to each of apartial sequence (1, −1) composed of two codes of the latter half of theorthogonal cover code sequence (1, −1, 1, −1) and a partial sequence(−1, 1) composed of two codes of the latter half of the orthogonal covercode sequence (1, −1, −1, 1).

That is, the orthogonal cover code sequence (1, 1, 1, 1) is partiallyorthogonal to the orthogonal cover code sequence (1, −1, 1, −1) and theorthogonal cover code sequence (1, −1, −1, 1). Between orthogonal covercode sequences which are partially orthogonal to each other, sequenceseach of which includes two symbols of the former half of four symbolscorresponding to a sequence length (sequences each of which is composedof two codes of the former half) are orthogonal to each other, andsequences each of which includes two symbols of the latter half(sequences each of which is composed of the two codes of the latterhalf) are also orthogonal to each other.

That is, terminal 200 (spreading section 215) spreads an ACK/NACK signalusing any of such a plurality of orthogonal cover code sequences thattheir partial sequences each of which is composed of codes correspondingto the first two symbols of a subframe (sequences each of whichcorresponds to two symbols of the former half) are mutually partiallyorthogonal, and their partial sequences each of which is composed ofcodes corresponding to the last two symbols (sequences each of whichcorresponds to two symbols of the latter half) are mutually partiallyorthogonal.

Thereby, by separating two-symbol former halves and two-symbol latterhalves, base station 100 can separate a plurality of ACK/NACK signalscode-multiplexed by orthogonal cover code sequences. Therefore, even ifthe last two SC-FDMA symbols (Method 1) or the first two SC-FDMA symbols(Method 2) are punctured in a retuning subframe to transmit a signal,collapse of orthogonality does not occur between orthogonal cover codesequences which are mutually partially orthogonal to each other. Inother words, even if any one of the sequence of the former-half twosymbols among four symbols corresponding to a sequence length and thesequence of the latter-half two symbols is punctured, collapse oforthogonality does not occur in the other sequence.

Here, for example, an orthogonal cover code sequence to be used in anexisting LTE terminal (an OCC sequence) is derived from a PUCCH resourceindex with the following equations.

$\begin{matrix}\lbrack 1\rbrack & \; \\{\mspace{250mu}{n_{OC} = \left\lfloor {n^{\prime} \cdot {\Delta_{shift}^{PUCCH}/N^{\prime}}} \right\rfloor}} & (1) \\\lbrack 2\rbrack & \; \\{\mspace{146mu}{N^{\prime} = \left\{ {{\begin{matrix}N_{CS}^{(1)} & {{{if}\mspace{14mu} n_{PUCCH}^{(1)}} < {c \cdot {N_{CS}^{(1)}/\Delta_{shift}^{PUCCH}}}} \\N_{SC}^{RB} & {otherwise}\end{matrix}\mspace{349mu} c} = 3} \right.}} & (2) \\\lbrack 3\rbrack & \; \\{n^{\prime} = \left\{ \begin{matrix}n_{PUCCH}^{(1)} & \begin{matrix}{{{if}\mspace{14mu} n_{PUCCH}^{(1)}} < {c \cdot}} \\{N_{CS}^{(1)}/\Delta_{shift}^{PUCCH}}\end{matrix} \\{\left( {n_{PUCCH}^{(1)} - {c \cdot {N_{CS}^{(1)}/\Delta_{shift}^{PUCCH}}}} \right){{mod}\left( {c \cdot {N_{SC}^{RB}/\Delta_{shift}^{PUCCH}}} \right)}} & {otherwise}\end{matrix} \right.} & (3)\end{matrix}$

In equations 1 to 3, noc indicates an OCC index; noc=0 indicates (1, 1,1, 1); noc=1 indicates (1, −1, 1, −1); and noc=2 indicates (1, −1, −1,1). Further, Δ_(shift) ^(PUCCH) indicates a gap between adjacent amountsof cyclic shift; N_(CS) ⁽¹⁾ indicates an amount of cyclic shift used forPUCCH format 1/1a/1b; N_(CS) ^(RB) indicates the number of subcarriersper one RB; and n_(PUCCH) ⁽¹⁾ indicates a PUCCH resource index.

Further, in the above equation, c=3 indicates the number of terminalswhich can be multiplexed by an orthogonal cover code sequence, that is,the number of candidates for an orthogonal cover code sequence to spreadan ACK/NACK signal. Therefore, in the present embodiment, c=2 is assumedin the above equation as the number of terminals 200 (MTC terminals) towhich frequency hopping is to be applied, and the number of candidatesfor an orthogonal cover code sequence to spread an ACK/NACK signal canbe restricted to two by deriving OCC indices from PUCCH resourceindices.

As described above, in the present embodiment, in the case wherefrequency hopping is applied at the time of uplink repetitiontransmission, terminal 200 punctures the last two SC-FDMA symbols or thefirst two SC-FDMA symbols of a retuning subframe to transmit a signal.At this time, terminal 200 restricts an orthogonal cover code sequenceto spread an ACK/NACK signal in a PUCCH to two orthogonal cover codesequences which are partially orthogonal to each other. Thereby, it ispossible to secure retuning time for changing the 1.4-MHz frequency bandwhich terminal 200 uses to transmit a repetition signal, without causingcollapse of orthogonality due to puncture to occur. Therefore, accordingto the present embodiment, it is possible to secure retuning time whilesuppressing deterioration of transmission characteristics of an uplinksignal (PUSCH or PUCCH).

Embodiment 2

Since basic configurations of a base station and a terminal according tothe present embodiment are the same as those of base station 100 andterminal 200 according to Embodiment 1, the base station and theterminal will be described with reference to FIGS. 9 and 10 again.

In the present embodiment, Method 3 (FIG. 6) among Methods 1 to 4 forsecuring retuning time described above will be used. In other words, inthe case of switching a narrowband to be used by frequency hopping,terminal 200 (control section 209) discards (punctures) the last SC-FDMAdata symbol of one subframe immediately before retuning and the firstSC-FDMA data symbol of one subframe immediately after retuning to usethe SC-FDMA data symbols for retuning time.

Base station 100 indicates terminal 200 of the number of PUSCHrepetitions (N_(PUSCH)) or the number of PUCCH repetitions (N_(PUCCH))in advance before PUSCH or PUCCH transmission/reception. The number ofrepetitions N_(PUSCH) or N_(PUCCH) may be indicated to terminal 200 frombase station 100 via a UE-specific higher layer or may be indicatedusing PDCCH for MTC.

Further, base station 100 indicates terminal 200 of a frequency hoppingmethod (on/off of frequency hopping and a frequency hopping period Y)before PUSCH or PUCCH transmission/reception. The frequency hoppingperiod Y may be indicated to terminal 200 via a cell-specific higherlayer by base station 100 as a cell-specific parameter or indicated toterminal 200 via a UE-specific higher layer by base station 100 as aUE-specific parameter. Further, the frequency hopping period Y may be aparameter predefined according to standards.

Terminal 200 performs repetition transmission of a PUSCH or a PUCCH thenumber of times corresponding to the number of repetitions indicatedfrom base station 100 (N_(PUSCH) or N_(PUCCH)).

Further, if frequency hopping is on, and the number of repetitions(N_(PUSCH) or N_(PUCCH)) is larger than Y, terminal 200 changes the1.4-MHz frequency band which terminal 200 uses to transmit a repetitionsignal (performs frequency hopping) after transmitting a repetitionsignal in consecutive Y subframes using the same resources, andtransmits a repetition signal again in consecutive Y subframes using thesame resources. At the time of performing frequency hopping, terminal200 secures retuning time corresponding to two SC-FDMA data symbols inone subframe immediately before retuning and one subframe immediatelyafter retuning according to Method 3 (FIG. 6).

<In the Case of PUSCH Repetition>

At the time of PUSCH repetition, terminal 200 maps data to twelveSC-FDMA data symbols excluding DMRS's (see, for example, FIG. 1) in aretuning subframe (one subframe immediately before retuning and onesubframe immediately after retuning) and, after that, punctures twoSC-FDMA data symbols for retuning time (one SC-FDMA data symbol in eachretuning subframe).

Otherwise, terminal 200 maps the data to eleven SC-FDMA data symbolsexcluding DMRS's and one SC-FDMA data symbol for retuning time in theretuning subframe (rate matching).

<In the Case of PUCCH Repetition>

At the time of PUCCH repetition, terminal 200 spreads and maps anACK/NACK signal in a retuning subframe of a former half (one subframeimmediately before retuning) with a shortened PUCCH format specified inRel-12 and, after that, punctures the last SC-FDMA symbol for retuningtime.

On the other hand, terminal 200 spreads the ACK/NACK signal in aretuning subframe of a latter half (one subframe immediately afterretuning) with a shortened PUCCH format specified in Rel-12 and, afterthat, maps the spread ACK/NACK signal to seven SC-FDMA symbols excludingthe first SC-FDMA symbol for retuning time and DMRS's.

That is, terminal 200 (spreading section 215) spreads the ACK/NACKsignal mapped to retuning subframes of the former half and the latterhalf with the shortened PUCCH format. Then, terminal 200 (transmittingsection 220) transmits the ACK/NACK signal mapped according to theshortened PUCCH format in the retuning subframe of the former half, andtransmits the ACK/NACK signal in symbols other than the first symbol, inthe retuning subframe of the latter half.

FIG. 12 shows a state of frequency hopping in PUCCH repetition in thecase of Method 3 and Y=4. As shown in FIG. 12, upon transmission of arepetition signal in consecutive subframes of Y=4, terminal 200 changesa frequency band by frequency hopping and transmits a repetition signalagain in consecutive four subframes. At this time, terminal 200punctures the last SC-FDMA symbol of one subframe immediately beforeretuning and the first SC-FDMA data symbol of one subframe immediatelyafter retuning.

Further, as shown in FIG. 12, in the retuning subframe of the formerhalf, the ACK/NACK signal is spread and mapped with the shortened PUCCHformat. In the shortened PUCCH format, an ACK/NACK signal is spread witha Walsh sequence with a sequence length of 4, which is the same sequencelength as the normal PUCCH format in a former-half slot of a subframe,and the ACK/NACK signal is spread with a DFT sequence with a sequencelength of 3 in a latter-half slot of the subframe. Therefore, in the onesubframe (fourteen symbols), a total number of symbols of the spreadACK/NACK signal (seven symbols) and DMRS's (six symbols) is thirteensymbols. In other words, by using the shortened PUCCH format, the lastsymbol of the one subframe is not used and can be secured as one symbolfor retuning time.

On the other hand, in the retuning subframe of the latter half, theACK/NACK signal is spread with a Walsh sequence with a sequence lengthof 4 and a DFT sequence with a sequence length of 3, similarly to theshortened PUCCH format, as shown in FIG. 12. Terminal 200 maps thespread ACK/NACK signal to seven SC-FDMA symbols excluding the firstSC-FDMA symbol for retuning time and DMRS's (six symbols). At this time,terminal 200 performs mapping of the ACK/NACK signal which has beenspread, in the retuning subframe of the latter half, the mapping beingperformed similarly among terminals. Thereby, base station 100 canseparate a plurality of response signals which have beencode-multiplexed by orthogonal cover code sequences (Walsh sequences andDFT sequences) in retuning subframes in latter halves.

Next, methods for mapping a spread ACK/NACK signal in a retuningsubframe of a latter half will be described.

FIG. 13 shows Mapping Examples 1 to 3 for an ACK/NACK signal.

In Mapping Example 1, terminal 200 changes (reverses) order of portionsof an ACK/NACK signal which has been spread with the shortened PUCCHformat and maps the ACK/NACK signal portions to seven SC-FDMA symbolsexcluding the first SC-FDMA symbol and DMRS's.

In Mapping Example 2, terminal 200 keeps the order of the portions ofthe ACK/NACK signal which has been spread with the shortened PUCCHformat as it is and maps the ACK/NACK signal portions to seven SC-FDMAsymbols excluding the first SC-FDMA symbol and DMRS's. In other words,in comparison with the mapping with the shortened PUCCH format, thesymbols of the spread ACK/NACK signal are shifted by one symbol.

In Mapping Example 3, terminal 200 exchanges a former-half slot and alatter-half slot of the ACK/NACK signal which has been spread with theshortened PUCCH format, with each other and, after that, changes(reverses) order of the portions (S′₀, S′₁, S′₂) of the ACK/NACK signalwhich has been spread in the former-half slot and maps the portions tothree SC-FDMA symbols excluding the first SC-FDMA symbol and DMRS's.

Methods for mapping an ACK/NACK signals which has been spread, in aretuning subframe of a latter half have been described above. The methodfor mapping an ACK/NACK signal which has been spread, in a retuningsubframe of a latter half is not limited to Mapping Examples 1 to 3described above. It is only necessary that the method is the same amongterminals 200 in which mapping of an ACK/NACK signal in a retuningsubframe of a latter half is code-multiplexed.

Thus, in the present embodiment, since a symbol which is not used formapping of an ACK/NACK signal and DMRS's in the shortened PUCCH formatis used for retuning time in a retuning subframe of a former half,collapse of orthogonality between orthogonal cover code sequences doesnot occur. Further, in a retuning subframe of a latter half, since theACK/NACK signal is spread similarly to the shortened PUCCH format andmapped to symbols other than the first SC-FDMA data symbol and DMRS's,collapse of orthogonality between orthogonal cover code sequences doesnot occur. Therefore, collapse of orthogonality between orthogonal covercode sequences does not occur in each retuning subframe.

Further, in the present embodiment, since use of orthogonal cover codesequences (OCC sequences) is not restricted, the maximum number ofterminals which can be multiplexed by an orthogonal cover code sequencecan be kept at three (that is, c=3 in equation 2), which is the same asthe number in the case of existing LTE terminals.

Embodiment 3

Since basic configurations of a base station and a terminal according tothe present embodiment are the same as those of base station 100 andterminal 200 according to Embodiment 1, the base station and theterminal will be described with reference to FIGS. 9 and 10 again.

In the present embodiment, Method 3 (FIG. 6), among Methods 1 to 4 forsecuring retuning time described above, will be used. In other words, inthe case of switching a narrowband to be used by frequency hopping,terminal 200 (control section 209) discards (punctures) the last SC-FDMAdata symbol of one subframe immediately before retuning and the firstSC-FDMA data symbol of one subframe immediately after retuning to usethe SC-FDMA data symbols for retuning time.

The present embodiment is different from Embodiment 2 only in processingfor an ACK/NACK signal in one subframe immediately after retuning (aretuning subframe of a latter half). Therefore, description of operationbefore PUSCH or PUCCH transmission/reception and operation at the timeof PUSCH repetition will be omitted here.

In the present embodiment, at the time of PUCCH repetition, terminal 200spreads and maps an ACK/NACK signal in a retuning subframe of a formerhalf (one subframe immediately before retuning) with a shortened PUCCHformat specified in Rel-12 and, after that, punctures the last SC-FDMAsymbol for retuning time.

On the other hand, terminal 200 spreads the ACK/NACK signal in aretuning subframe of a latter half (one subframe immediately afterretuning) with the shortened PUCCH format specified in Rel-12 and, afterthat, punctures the last SC-FDMA symbol. Further, in the presentembodiment, terminal 200 adds a timing offset corresponding to onesymbol to a transmission timing of a retuning subframe of a latter half.

FIG. 14 shows a state of frequency hopping in PUCCH repetition in thecase of Method 3 and Y=4. As shown in FIG. 14, upon transmission of arepetition signal in consecutive subframes of Y=4, terminal 200 changesa frequency band by frequency hopping and transmits a repetition signalagain in consecutive four subframes. At this time, terminal 200punctures the last SC-FDMA symbol of one subframe immediately beforeretuning and the first SC-FDMA data symbol of one subframe immediatelyafter retuning.

Further, as shown in FIG. 14, in a retuning subframe of a former half,an ACK/NACK signal is mapped with the shortened PUCCH format similarlyto Embodiment 2. Therefore, as shown in FIG. 14, in the retuningsubframe of the former half, the last SC-FDMA symbol to which the signalis not mapped in the shortened PUCCH format can be secured for retuningtime.

On the other hand, in a retuning subframe of a latter half, the ACK/NACKsignal is spread with a Walsh sequence with a sequence length of 4 and aDFT sequence with a sequence length of 3, similarly to the shortenedPUCCH format, as shown in FIG. 14. Further, terminal 200 adds a timingoffset corresponding to one SC-FDMA symbol to a transmission timing ofthe retuning subframe of the latter half. As a result, in the retuningsubframe of the latter half, the signal in the shortened PUCCH format istransmitted from the second symbol as shown in FIG. 14. Thereby, thefirst SC-FDMA symbol of the retuning subframe of the latter half can besecured for retuning time. Further, since the shortened PUCCH format isapplied as it is, in the retuning subframe of the latter half which isshown in FIG. 14, it is not necessary to specify a new PUCCH format, andit is also not necessary to change an ACK/NACK signal mapping method.

Thus, in the present embodiment, since a symbol which is not used formapping of an ACK/NACK signal and DMRS's in the shortened PUCCH formatis used for retuning time in a retuning subframe of a former half,collapse of orthogonality between orthogonal cover code sequences doesnot occur. Further, in a retuning subframe of a latter half, since theACK/NACK signal is spread similarly to the shortened PUCCH format, andthe signal is transmitted, with a timing offset corresponding to oneSC-FDMA symbol added to the signal. Thereby, even if a symbol forretuning is secured, a signal in the shortened PUCCH format is kept asit is, and, therefore, collapse of orthogonality between orthogonalcover code sequences does not occur. Therefore, collapse oforthogonality between orthogonal cover code sequences does not occur ineach retuning subframe.

Further, in the present embodiment, since use of orthogonal cover codesequences (OCC sequences) is not restricted, the maximum number ofterminals which can be multiplexed by an orthogonal cover code sequencecan be kept at three (that is, c=3 in equation 2), which is the same asthe number in the case of existing LTE terminals.

[Modifications of Embodiment 2 or 3]

In Embodiments 2 and 3, description has been made on a case where theshortened PUCCH format or the shortened PUCCH format in which mapping ispartially changed is used as a format for transmitting an ACK/NACKsignal in a retuning subframe. In comparison, in the presentmodification, in the case where frequency hopping is applied to uplinktransmission, terminal 200 performs PUCCH repetition transmission usingthe shortened PUCCH format or the shortened PUCCH format in whichmapping is partially changed not only for a retuning subframe but alsofor all subframes to which repetition is applied.

FIG. 15 shows a state of frequency hopping in PUCCH repetition in thecase of Y=4.

As shown in FIG. 15, upon transmission of a repetition signal inconsecutive subframes of Y=4, terminal 200 changes a frequency band byfrequency hopping and transmits a repetition signal again in consecutivefour subframes. At this time, the shortened PUCCH format is used for allfour subframes before retuning, and the shortened PUCCH format in whichmapping is partially changed is used for all four subframes afterretuning.

Thereby, ACK/NACK signals are multiplied by the same OCC sequence in theretuning subframe and the other subframes, and, therefore, base station100 can perform channel estimation and symbol level combination for aplurality of subframes in units of Y subframes. In other words, it canbe prevented that an ACK/NACK signal is multiplied by different OCCsequences in the retuning subframe and in the other subframes(specifically, a DFT sequence in the retuning subframe and a Walshsequence in the other subframes), and, thereby, coherent combining ofsignal portions before being despread cannot be performed on basestation 100 side, so that a demodulation process is complicated.

Embodiment 4

If a terminal transmits a PUCCH and a PUSCH in consecutive subframes,and a 1.4-MHz frequency band (narrowband) for PUCCH transmission and a1.4-MHz frequency band (narrowband) for PUSCH transmission aredifferent, retuning is required between PUCCH transmission and PUSCHtransmission.

In Embodiments 1 to 3, description has been made on retuning infrequency hopping in the case of performing repetition transmission of aPUSCH or a PUCCH. In comparison, in the present embodiment, descriptionwill be made on retuning in PUCCH transmission after PUSCH transmissionor in PUSCH transmission after PUCCH transmission.

Since basic configurations of a base station and a terminal according tothe present embodiment are the same as those of base station 100 andterminal 200 according to Embodiment 1, the base station and theterminal will be described with reference to FIGS. 9 and 10 again.

In the present embodiment, Method 1 (FIG. 4) and Method 2 (FIG. 5) amongMethods 1 to 4 for securing retuning time described above will be used.In other words, in the case of switching a narrowband to be used byfrequency hopping, terminal 200 may discard the last two SC-FDMA datasymbols of one subframe immediately before retuning to use the SC-FDMAdata symbols for retuning time or may discard the first two SC-FDMA datasymbols of one subframe immediately after retuning to use the SC-FDMAdata symbols for retuning time.

In the present embodiment, if PUSCH transmission and PUCCH transmissionare performed in consecutive subframes, retuning for changing the1.4-MHz frequency band for transmission of terminal 200 can be securedwithout causing collapse of orthogonality between orthogonal cover codesequences to occur, by setting a retuning subframe similarly toEmbodiment 1 (for example, FIG. 11).

In the present embodiment, base station 100 notifies terminal 200 of thenumber of PUSCH repetitions (N_(PUSCH)) or the number of PUCCHrepetitions (N_(PUCCH)) in advance before PUSCH or PUCCHtransmission/reception. The number of repetitions N_(PUSCH) or N_(PUCCH)may be indicated to terminal 200 from base station 100 via a UE-specifichigher layer or may be indicated using a PDCCH for MTC.

Terminal 200 performs PUSCH or PUCCH repetition transmission the numberof times corresponding to the number of repetitions indicated from basestation 100 (N_(PUSCH) or N_(PUCCH)).

Further, in a case where PUCCH repetition transmission is to beperformed from a subframe next to a subframe for which PUSCH repetitiontransmission has ended, and the 1.4-MHz frequency band for PUSCHtransmission and the 1.4-MHz frequency band for PUCCH transmission aredifferent, terminal 200 punctures the last two SC-FDMA symbols of aPUSCH subframe immediately before retuning according to Method 1 (seeFIG. 4) to secure the SC-FDMA symbols for retuning time as shown in FIG.16.

On the other hand, in a case where PUSCH repetition transmission is tobe performed from a subframe next to a subframe for which PUCCHrepetition transmission has ended, and the 1.4-MHz frequency band forPUSCH transmission and the 1.4-MHz frequency band for PUCCH transmissionare different, terminal 200 punctures the first two SC-FDMA symbols of aPUSCH subframe immediately after retuning according to Method 2 (seeFIG. 5) to secure the SC-FDMA symbols for retuning time as shown in FIG.17.

That is, if retuning is required immediately before PUCCH repetitiontransmission, terminal 200 discards the last two SC-FDMA symbols of onesubframe immediately before PUCCH repetition is started to secure theSC-FDMA symbols for retuning time. Further, if retuning is requiredimmediately after PUCCH repetition transmission, terminal 200 discardsthe first two SC-FDMA symbols of one subframe immediately after PUCCHrepetition ends to secure the SC-FDMA symbols for retuning time.

In other words, in the case where PUSCH repetition transmission andPUCCH repetition transmission are performed in consecutive subframes,and the 1.4-MHz frequency band is different between PUSCH transmissionand PUCCH transmission, terminal 200 punctures two SC-FDMA symbolsimmediately before (FIG. 16) or immediately after (FIG. 17) the 1.4-MHzfrequency band (narrowband) in a subframe in which a PUSCH istransmitted is switched to secure retuning time.

Thus, by setting a retuning subframe on the PUSCH side when PUSCHtransmission and PUCCH transmission are consecutively performed, thefollowing problem can be solved.

First, description will be made on retuning from PUSCH transmission toPUCCH transmission shown in FIG. 16.

At the time of retuning, base station 100 has already transmitted anuplink grant indicating PUSCH assignment, to terminal 200 via a downlinkcontrol channel for MTC before a PUSCH is transmitted/received.

If the uplink grant can be correctly decoded, terminal 200 can transmitthe PUSCH. In this case, if PUCCH transmission is performed in asubsequent subframe after the PUSCH transmission, terminal 200 performsretuning and then starts the PUCCH transmission. Therefore, retuningtime is required between the PUSCH transmission and the PUCCHtransmission.

On the other hand, if the uplink grant cannot be correctly decoded,terminal 200 does not transmit the PUSCH. In this case, since PUSCHtransmission immediately before PUCCH transmission is not performed,terminal 200 does not have to perform retuning immediately before thePUCCH transmission. In such a case, if a retuning subframe is set on thePUCCH side, base station 100 assumes that a first subframe of PUCCHrepetition is a retuning subframe, while terminal 200 actually sets thefirst subframe of the PUCCH repetition similarly to an ordinary subframeto transmit an ACK/NACK signal. Therefore, in the first subframe of thePUCCH repetition, a mismatch occurs between a PUCCH which base station100 assumes and a PUCCH which terminal 200 actually transmits.

In comparison, in the present embodiment, in the case where PUCCHtransmission is performed in a subsequent subframe after PUSCHtransmission, a retuning subframe is set only on the PUSCH side.Thereby, it is possible to always use the first subframe of PUCCHrepetition as an ordinary subframe without depending on whether decodingof an uplink grant is successful or not. Therefore, a mismatch relatedto a PUCCH does not occur between base station 100 and terminal 200.Further, since a retuning subframe is set only on the PUSCH side, itdoes not happen that setting of retuning time influences onorthogonality of OCC sequences in a PUCCH.

Next, description will be made on retuning from PUCCH transmission toPUSCH transmission shown in FIG. 17.

Retuning from PUCCH transmission to PUSCH transmission can be thoughtsimilarly to retuning from PUSCH transmission to PUCCH transmission. Inother words, base station 100 has transmitted an uplink grant indicatingPUSCH assignment, to terminal 200 via a downlink control channel for MTCbefore a PUSCH is transmitted/received.

If the uplink grant can be correctly decoded, terminal 200 can transmitthe PUSCH. In this case, if PUSCH transmission is performed in asubsequent subframe after the PUCCH transmission, terminal 200 performsretuning and then starts the PUSCH transmission. Therefore, retuningtime is required between the PUCCH transmission and the PUSCHtransmission.

On the other hand, if the uplink grant cannot be correctly decoded,terminal 200 does not transmit the PUSCH. In this case, since PUSCHtransmission immediately after PUCCH transmission is not performed,terminal 200 does not have to perform retuning immediately after thePUCCH transmission. In such a case, if a retuning subframe is set on thePUCCH side, base station 100 assumes that a last subframe of PUCCHrepetition is a retuning subframe, while terminal 200 actually sets thelast subframe of PUCCH repetition similarly to an ordinary subframe totransmit an ACK/NACK signal. Therefore, in the last subframe of PUCCHrepetition, a mismatch occurs between a PUCCH which base station 100assumes and a PUCCH which terminal 200 actually transmits.

In comparison, in the present embodiment, in the case where PUSCHtransmission is performed in a subsequent subframe after PUCCHtransmission, a retuning subframe is set only on the PUSCH side.Thereby, it is possible to always use the last subframe of PUCCHrepetition as an ordinary subframe without depending on whether decodingof an uplink grant is successful or not. Therefore, a mismatch relatedto a PUCCH does not occur between base station 100 and terminal 200.Further, since a retuning subframe is set only on the PUSCH side, itdoes not happen that setting of retuning time influences orthogonalityof an OCC of a PUCCH.

Embodiment 5

Since basic configurations of a base station and a terminal according tothe present embodiment are the same as those of base station 100 andterminal 200 according to Embodiment 1, the base station and theterminal will be described with reference to FIGS. 9 and 10 again.

In a method for securing retuning time based on any of Methods 1 to 3described in Embodiments 1 to 4, resource use efficiency in terminal 200can be improved in comparison with Method 4 in which a guard subframe(one subframe) is provided for retuning. When a frequency hopping periodis Y subframes, the resource use efficiency in Method 4 is (Y−1)/Y. Onthe other hand, the resource use efficiency in Methods 1 to 3 is(Y−1+(12/14))/Y. For example, in the case of Y=4, the resource useefficiency can be improved by 28% according to Methods 1 to 3 incomparison with Method 4.

On the other hand, in the case of a PUCCH, it is possible to cause aplurality of terminals 200 to be multiplexed within the sametime/frequency resources by an OCC (Orthogonal Cover Code) sequence.Therefore, in addition to the resource use efficiency in terminals 200,resource use efficiency in a network is also an important indicator.

The PUCCH resource use efficiency in a network is obtained bymultiplying the resource use efficiency in terminal 200 by the number ofterminals which can be multiplexed by an orthogonal cover code sequence(for example, c in equation 2). In other words, the PUCCH resource useefficiency in a network is 2×(Y−1+(12/14))/Y in Embodiments 1 and 4(Method 1 or 2; c=2) and 3×(Y−1+(12/14))/Y in Embodiments 2 and 3(Method 3; c=3). On the other hand, the PUCCH resource use efficiency ina network in Method 4, that is, in the case of providing a guardsubframe (one subframe) for retuning is 3×(Y−1)/Y.

From the above, it can be said that the PUCCH resource use efficiency ina network is the largest in Embodiments 2 and 3. On the other hand, inEmbodiment 1 or 4, the number of terminals which can be multiplexed byan OCC is not three but restricted to two, and, therefore, the PUCCHresource use efficiency in a network decreases.

Specifically, the PUCCH resource use efficiency in a network in themethod of Embodiment 1 is 2×(Y−1+(12/14))/Y, and the PUCCH resource useefficiency in a network in Method 4 (a method in which a guard subframeis provided for retuning) is 3×(Y−1)/Y as described above. Therefore,when both resource use efficiencies are compared, the PUCCH resource useefficiency in a network in Method 4 is larger than that in the method ofEmbodiment 1 in the case of Y>2.72, that is, when the frequency hoppingperiod Y is 3 or larger.

Therefore, in the present embodiment, description will be made on a casewhere the method of Embodiment 1 and Method 4 (a method in which a guardsubframe is provided for retuning) are used together in consideration ofthe PUCCH resource use efficiency in a network. Specifically, terminal200 switches between the method of Embodiment 1 and Method 4 (a methodin which a guard subframe is provided for retuning) according to afrequency hopping period.

FIG. 18 shows a state of frequency hopping in PUCCH repetition in thecase of Y=2 (<3), and FIG. 19 shows a state of frequency hopping inPUCCH repetition in the case of Y=4 (≤3).

As shown in FIG. 18, if the frequency hopping period is below 3,terminal 200 uses the method of Embodiment 1, that is, punctures thelast two SC-FDMA symbols of a subframe immediately before retuning tosecure retuning time. On the other hand, as shown in FIG. 19, if thefrequency hopping period is 3 or more, terminal 200 does not puncturethe two SC-FDMA symbols described above but uses Method 4, that is,provides a guard subframe between subframes before and after retuning tosecure retuning time.

Thus, by switching between methods for securing retuning time accordingto a frequency hopping period, terminal 200 can optimize the PUCCHresource use efficiency in a network. Further, in Method 4, since thewhole of the retuning subframe is discarded, collapse of orthogonalityof a PUCCH is not caused.

Which method (the method of Embodiment 1 or Method 4) is to be used isnot limited to the case where terminal 200 decides which method is to beused based on a frequency hopping period. For example, base station 100may indicate terminal 200 about which method (the method of Embodiment 1or Method 4) is to be used via a cell-specific higher layer or aUE-specific higher layer.

Further, operation of terminal 200 deciding which method (the method ofEmbodiment 1 or Method 4) is to be used may be operation predefinedaccording to standards. For example, if terminal 200 is in a coverageenhancement mode A (no/small repetition) (that is, the number ofsubframes to be repeated is small), it is assumed that a frequencyhopping period is short, and, therefore, the method of Embodiment 1 isused. If terminal 200 is in a coverage enhancement mode B (largerepetition) (that is, the number of subframes to be repeated is large),it is assumed that a frequency hopping frequency is long, and,therefore, it is also possible to use Method 4.

Further, a threshold Y_(th) for switching a method for securing retuningtime may be set as a parameter. Here, Y_(th) may be notified to terminal200 by base station 100 via a cell-specific higher layer as acell-specific parameter or indicated to terminal 200 by base station 100via a UE-specific higher layer as a UE-specific parameter. Further,Y_(th) may be a parameter predefined according to standards.

Embodiment 6

In a PUCCH, not only transmission of an ACK/NACK signal but alsotransmission of CSI feedback, which is periodically transmitted on anuplink, is performed. In the case of transmissions of the CSI feedback,or when transmission of the CSI feedback and transmission of an ACK/NACKsignal overlap, a PUCCH format 2/2a/2b is used. FIG. 20 shows aconfiguration example of a PUCCH format 2/2a/2b subframe. As shown inFIG. 20, two DMRS's and five SC-FDMA data symbols (CSI feedbackinformation) are time-multiplexed in each slot.

Therefore, in the present embodiment, operation of retuning for thePUCCH format 2/2a/2b will be described.

Repetition transmission of the PUCCH format 2/2a/2b is not assumed.Operation in a case where repetition transmission using the PUCCH format1/1a/1b or PUSCH repetition transmission, and transmission using thePUCCH format 2/2a/2b occur in consecutive subframes will be describedbelow as an example.

If the last two SC-FDMA symbols of one subframe immediately beforeretuning or at the first two SC-FDMA symbols of one subframe immediatelyafter retuning are punctured as in Method 1 (FIG. 4) or Method 2 (FIG.5) when a subframe using the PUCCH format 2/2a/2b is a retuningsubframe, DMRS's are punctured. In this case, base station 100 cannotuse the DMRS's, and, therefore, demodulation becomes difficult.

Therefore, in the present embodiment, if retuning is required before andafter transmission using the PUCCH format 2/2a/2b, terminal 200 dropsone subframe of any one of the channels before and after retuning.

Which of the channels before and after retuning is to be prioritized (orto be dropped) depends on norms of priority. For example, in the currentstandards, priority order is generally ACK/NACK signal>PUSCH>periodicalCSI. In this case, the PUCCH format 2/2a/2b immediately before orimmediately after retuning is dropped because its priority is low.

By dropping any one of the channels according to priority as describedabove, it is possible to prevent influence on a higher-priority channelin retuning. For example, if priority of ACK/NACK signal is increased,it is possible to prevent influence of dropping on the PUCCH format1/1a/1b, and, therefore, collapse of orthogonality of a PUCCH is notcaused. Even if priority of ACK/NACK signal is decreased on thecontrary, the whole subframe of the ACK/NACK signal is discarded, and,therefore, orthogonality of a PUCCH is not influenced.

In the case where retuning is required before and after transmissionusing the PUCCH format 2/2a/2b, Method 3 (FIG. 6) may be applied. Inother words, terminal 200 may puncture the last symbol of one subframeimmediately before retuning and the first symbol of one subframeimmediately after retuning. In this case, even if a subframe using thePUCCH format 2/2a/2b becomes a retuning subframe, DMRS's are notpunctured. Therefore, puncture does not influence demodulation in basestation 100.

Each embodiment of the present disclosure has been described above.

Though, in the above embodiments, description has been made on a casewhere an aspect of the present disclosure is implemented by hardware,the present disclosure can be realized by software in cooperation withhardware.

Further, each functional block used in the description of the aboveembodiments is typically realized as an LSI which is an integratedcircuit. The integrated circuit controls each functional block used inthe description of the above embodiments and may be provided with aninput and an output. These may be individually integrated into one chip,or a part or all of them may be into one chip so that the part or all ofthem are included. Though the integrated circuit is assumed to be an LSIhere, it may also be referred to as an IC, system LSI, super LSI orultra LSI according to difference in a degree of integration.

Further, a scheme for integrated circuitization is not limited to anLSI, but the integrated circuit may be realized by a dedicated circuitor a general-purpose processor. An FPGA (Field Programmable Gate Array)which can be programmed after manufacture of an LSI or a reconfigurableprocessor in which connections and settings of circuit cells inside theLSI can be reconfigured may be used.

Furthermore, if an integrated circuitization technology which replacesthe LSI appears due to progress in semiconductor technology or otherderived technologies, integration of the functional blocks may be, ofcourse, performed using the technology. Application of biotechnology andthe like can be possibilities.

A terminal of the present disclosure is provided with: a control sectionthat, if, for a narrowband to be used for a subframe to transmit uplinkdata, switching from a first narrowband used for a first subframe to asecond narrowband different from the first narrowband, for a secondsubframe following the first subframe, punctures a last one symbol ofthe first subframe and a first one symbol of the second subframe to setthe symbols as retuning time; and a transmitting section that transmitsthe uplink data in the first narrowband and the second narrowband.

A terminal of the present disclosure is provided with: a control sectionthat, if switching from a first narrowband used for a first subframe totransmit ACK/NACK to downlink data to a second narrowband different fromthe first narrowband, for a second subframe to transmit uplink data, thesecond subframe following the first subframe, sets first two symbols ofthe second subframe as retuning time; and a transmitting section thattransmits the ACK/NACK in the first narrowband and transmits the uplinkdata in the second narrowband.

A terminal of the present disclosure is provided with: a control sectionthat, if switching from a first narrowband used for a first subframe totransmit uplink data to a second narrowband different from the firstnarrowband, for a second subframe to transmit ACK/NACK to downlink data,the second subframe following the first subframe, sets last two symbolsof the first subframe as retuning time; and a transmitting section thattransmits the uplink data in the first narrowband and transmits theACK/NACK in the second narrowband.

A terminal of the present disclosure is provided with: a control sectionthat, if, for a narrowband to be used for a subframe to transmitfeedback of CSI (Channel State Information) using a PUCCH (PhysicalUplink Control Channel) format 2a/2b, switching from a first narrowbandused for a first subframe to a second narrowband different from thefirst narrowband, for a second subframe following the first subframe,punctures a last one symbol of the first subframe and a first one symbolof the second subframe to set the symbols as retuning time; and atransmitting section that transmits the CSI signal in the firstnarrowband and the second narrowband.

In the terminal of the present disclosure, the control section switchesfrom the first narrowband to the second narrowband by frequency hopping.

In the terminal of the present disclosure, the first narrowband and thesecond narrowband are set for MTC (Machine Type Communication)terminals.

A transmission method of the present disclosure includes: if, for anarrowband to be used for a subframe to transmit uplink data, a firstnarrowband used for a first subframe is switched to a second narrowbanddifferent from the first narrowband, for a second subframe following thefirst subframe, puncturing a last one symbol of the first subframe and afirst one symbol of the second subframe to set the symbols as retuningtime; and transmitting the uplink data in the first narrowband and thesecond narrowband.

A transmission method of the present disclosure includes: if a firstnarrowband used for a first subframe to transmit ACK/NACK to downlinkdata is switched to a second narrowband different from the firstnarrowband, for a second subframe to transmit uplink data, the secondsubframe following the first subframe, setting first two symbols of thesecond subframe as retuning time; and transmitting the ACK/NACK in thefirst narrowband and transmitting the uplink data in the secondnarrowband.

A transmission method of the present disclosure includes: if a firstnarrowband used for a first subframe to transmit uplink data is switchedto a second narrowband different from the first narrowband, for a secondsubframe to transmit ACK/NACK to downlink data, the second subframefollowing the first subframe, setting last two symbols of the firstsubframe as retuning time; and transmitting the uplink data in the firstnarrowband and transmitting the ACK/NACK in the second narrowband.

A transmission method of the present disclosure includes: if, for anarrowband to be used for a subframe to transmit feedback of CSI using aPUCCH format 2a/2b, a first narrowband used for a first subframe isswitched to a second narrowband different from the first narrowband, fora second subframe following the first subframe, puncturing a last onesymbol of the first subframe and a first one symbol of the secondsubframe to set the symbols as retuning time; and transmitting the CSIsignal in the first narrowband and the second narrowband.

INDUSTRIAL APPLICABILITY

An aspect of the present disclosure is useful for a mobile communicationsystem.

REFERENCE SIGNS LIST

-   -   100 Base station    -   200 Terminal    -   101,209 Control section    -   102 Control signal generating section    -   103 Control signal encoding section    -   104 Control signal modulating section    -   105, 210 Data encoding section    -   106 Retransmission control section    -   107 Data modulating section    -   108, 217 Signal assigning section    -   109, 218 IFFT section    -   110, 219 CP adding section    -   111, 220 Transmitting section    -   112, 201 Antenna    -   113, 202 Receiving section    -   114, 203 CP removing section    -   115, 204 FFT section    -   116, 205 Extracting section    -   117 Demapping section    -   118 Channel estimating section    -   119 Equalizing section    -   120 Demodulating section    -   121 Decoding section    -   122, 125 Judging section    -   123 Despreading section    -   124 Correlation processing section    -   206 Data demodulating section    -   207 Data decoding section    -   208 CRC section    -   211 CSI signal generating section    -   212 Response signal generating section    -   213 Modulating section    -   214 DFT section    -   215 Spreading section    -   216 Repetition section

The invention claimed is:
 1. A communication apparatus comprising:circuitry, which, in operation, sets a retuning time, when retuning froma first narrowband for transmitting a first channel in a first subframeto a second narrowband for transmitting a second channel in a secondsubframe, the second subframe being consecutive to the first subframealong a time axis; and a transmitter, which, in operation, transmits thefirst channel and the second channel, wherein: when the first channeland the second channel are a PUCCH (Physical Uplink Control Channel) fortransmitting a channel state information (CSI), a last symbol of thefirst subframe and a first symbol of the second subframe are set as theretuning time, and at least one of the CSI is punctured for the retuningtime.
 2. The communication apparatus according to claim 1, wherein, whenthe first channel is the PUCCH for transmitting an ACK/NACK(Acknowledgement/Negative Acknowledgement) signal and the second channelis a PUSCH (Physical Uplink Shared Channel) for transmitting uplinkdata, first two symbols of the second subframe are set as the retuningtime.
 3. The communication apparatus according to claim 1, wherein, whenthe first channel is a PUSCH for transmitting uplink data and the secondchannel is the PUCCH for transmitting an ACK/NACK signal, last twosymbols of the first subframe are set as the retuning time.
 4. Thecommunication apparatus according to claim 1, wherein a frequencyhopping is used to retune from the first narrowband to the secondnarrowband.
 5. The communication apparatus according to claim 1,wherein, when the first channel and the second channel are the PUCCH fortransmitting an ACK/NACK signal, the last symbol of the first subframeand the first symbol of the second subframe are set as the retuningtime, the ACK/NACK signal being generated using a shortened PUCCH formatfor the retuning time.
 6. The communication apparatus according to claim1, wherein the first narrowband and the second narrowband are set forMTC (Machine Type Communication) terminals.
 7. The communicationapparatus according to claim 1, wherein the CSI is transmitted by usingPUCCH format 2, 2a or 2b.
 8. A communication method comprising: settinga retuning time, when retuning from a first narrowband for transmittinga first channel in a first subframe to a second narrowband fortransmitting a second channel in a second subframe, the second subframebeing consecutive to the first subframe along a time axis; andtransmitting the first channel and the second channel, wherein: when thefirst channel and the second channel are a PUCCH (Physical UplinkControl Channel) for transmitting a channel state information (CSI), alast symbol of the first subframe and a first symbol of the secondsubframe are set as the retuning time, and at least one of the CSI ispunctured for the retuning time.
 9. The communication method accordingto claim 8, wherein, when the first channel is the PUCCH fortransmitting an ACK/NACK (Acknowledgement/Negative Acknowledgement)signal and the second channel is a PUSCH (Physical Uplink SharedChannel) for transmitting uplink data, first two symbols of the secondsubframe are set as the retuning time.
 10. The communication methodaccording to claim 8, wherein, when the first channel is a PUSCH fortransmitting uplink data and the second channel is the PUCCH fortransmitting an ACK/NACK signal, last two symbols of the first subframeare set as the retuning time.
 11. The communication method according toclaim 8, wherein a frequency hopping is used to retune from the firstnarrowband to the second narrowband.
 12. The communication methodaccording to claim 8, wherein, when the first channel and the secondchannel are the PUCCH for transmitting an ACK/NACK signal, the lastsymbol of the first subframe and the first symbol of the second subframeare set as the retuning time, the ACK/NACK signal being generated usinga shortened PUCCH format for the retuning time.
 13. The communicationmethod according to claim 8, wherein the first narrowband and the secondnarrowband are set for MTC (Machine Type Communication) terminals. 14.The communication method according to claim 8, wherein the CSI istransmitted by using PUCCH format 2, 2a or 2b.